Re: microprocessor controlled SMPS

From: artem_bond (artem_bond_at_mail.ru)
Date: 06/08/04 

Date: 7 Jun 2004 17:26:54 -0700

kensmith@violet.rahul.net (Ken Smith) wrote in message news:<ca2dmk$4h7$1@blue.rahul.net>...
> In article <4bea06d1.0406070143.57cdef1f@posting.google.com>,
> artem_bond <artem_bond@mail.ru> wrote:
> >Hello all.
> >
> >I have a principal question about SMPS with microprocessor. SMPS
> >without microprocessor (UC3842) is simply. But I'm thinking about
> >putting feedback to the CPU, more protections from stupids and other
> >things. But, using microprocessor could be dangerous because it's
> >could be hang-up by EMI or errors in firmware.
>
> Hmmmmm.
>
> That you seem think units will ship with "errors in the firmware" is
> a bit scary. If you were doing it with Rs and Cs and op-amps, you
> wouldn't ship it with errors in the component values. The firmware for a
> switcher is going to be simple enough that you can prove it is correct.
>

Yes. But it's not only "simply" SMPS in this SMPS expected RS485 bus,
a lots displays, temperature controls in few points and others. If
course, I can use external interrupt for protection. It's fast and
simply. But, imagine 10kV discharge, 0.1mf capacitor near by CPU. It's
provide huge EMI and this EMI can come (en example) to crystal
resonator (most sensitive thing in CPU). CPU can do everything even
put 0xff value to PWM generator and hang-up after this. It's produce
through current and IGBT burn-out. By this I will make all protection
outside CPU.

> As to the real problem:
>
> If you want this supply to always come on and only want some of the tuning
> to be done by the micro, I suggest you look at the nonvolatile digital
> pots made by Dallas Semi and others. The micro can tune the values as
> needed and should the micro fail, in a way other than going crazy, the
> values will stay as set and no great harm will be done.

Yes, I thinking about it's. I'm working whith AD7376. It's worked
very well. But I thing that if a lots of invertors(?) (for regulate
frequency of rotation asynchronous motor) working well, making
reliable SMPS by this way is good idea. I just can't find any
appnotes. All only for three phase, and nothing for what I want.

>
> I suggest you pick your supply topology so that failure of the micro
> doesn't allow the output voltage to go very high. This argues against
> using a flyback design.
>

My main problem is protect SMPS. I did't worry about load. But load
can do everything. It's a one of benefit of using CPU: I can react on
short-currents much better.

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